Bayonet primers have long been used in tank ammunition. As noted in U.S. Pat. No. 5,465,665 to Diehl issued Nov. 14, 1995, entitled "Primer," a typical bayonet type primer includes a primer head for housing an initial firing stage of a round. An ignition element, pressed into place in the confines of the primer head, is charged with a pyrotechnic composition that starts the firing train. When activated, the ignition element disperses a flame through a retainer. The flame sets off an explosive charge of black powder. The black powder charge in turn propagates through a closing plug which acts as a directional device to a third charge of Benite. Benite is comprised mainly of nitrocellulose and black powder in a stranded form and other pyrotechnic formulations, housed in the primer body. The third charge propagates through holes in the metal primer body initially sealed with a lacquer. This charge, propagating through the primer body, ignites the propelling charge contained in the ammunition case moving the ammunition projectile such as a penetrator out of the gun barrel and to its target. U.S. Pat. No. 5,465,665 is incorporated in its entirety herein by reference.
Unfortunately, conventional primers require a fine thread for attaching a retaining ring and closing plug assembly into a primer head assembly. Use of such a fine thread attachment mechanism results in a complicated and cumbersome assembly procedure. During assembly, the retaining ring must initially be carefully aligned. Once aligned it must be threaded into the head assembly without cross threading, driven to a specified torque value, and then staked. Such a delicate process is very difficult to automate due to the tolerances involved.
The threads are coated with a lacquer to secure the threaded parts. Such use of lacquer for securing the thread closing plug assembly presents a process variable that is difficult to control in automated assembly environments. As is the case with the retaining ring, sensitive alignment, cross-threading and torque controls are required. As a further drawback of conventional primers, fine threads often gall and bind during the assembly, thus adding another failure mode in an assembly already prone to difficult processes.
In conventional primers, the load of a potential shock is born by the fine internal threads of the retaining ring holding in the press fit ignition element assembly. In such old configurations, the lacquer may fail to secure the parts, and the closing plug assembly can unscrew due to such shocks. A visual inspection of the primer tube would not show an external indication of a problem with such an unthreaded closing plug assembly.
For many years, typical prior art designs have included the threaded retaining ring juxtaposed between the closing plug assembly and the ignition element. Such retaining rings provided a mechanism for sealing parts. Retaining rings of prior art primers also formed a gap between the closing plug assembly and ignition element. The gap was thought necessary for the proper ignition of black powder held by the closing plug assembly.
In contrast to the prior art, it has been discovered that the black powder used in the closing plug assembly is not very sensitive to the configuration of the ignition mechanism. It has further been discovered that neither the gap provided by the retaining ring, nor the retaining ring itself, significantly effect the function of the primer ignition. The present invention takes advantage of these discoveries by providing an improved and simplified primer redesigned to eliminate the retaining ring and gap. The simplified primer of the present invention generates significant savings in manufacture by eliminating hard-to-handle small parts, complicated automated handling systems, difficult inspections, and scrap without significantly effecting primer ignition times.
Further in contrast to the prior art, a primer constructed in accordance with the present invention exhibits significant gains in safety because it can be ascertained that all parts are assembled correctly from a visual inspection of the exterior of a fully assembled primer. Further still, the primer of the present invention is less costly to manufacture due to the elimination of parts used in the prior art that are difficult to handle and assemble. Elimination of parts also reduces the administrative efforts of procurement, inspection, inventory, storage, scheduling and scrap. Further still, the present invention substantially reduces continuous maintenance of complicated and temperamental assembly machinery.